Commentary for Bava Batra 10:1
גֵּט פָּשׁוּט, עֵדָיו מִתּוֹכוֹ. וּמְקֻשָּׁר, עֵדָיו מֵאֲחוֹרָיו. פָּשׁוּט שֶׁכָּתְבוּ עֵדָיו מֵאֲחוֹרָיו וּמְקֻשָּׁר שֶׁכָּתְבוּ עֵדָיו מִתּוֹכוֹ, שְׁנֵיהֶם פְּסוּלִים. רַבִּי חֲנִינָא בֶן גַּמְלִיאֵל אוֹמֵר, מְקֻשָּׁר שֶׁכָּתְבוּ עֵדָיו מִתּוֹכוֹ, כָּשֵׁר, מִפְּנֵי שֶׁיָּכוֹל לַעֲשׂוֹתוֹ פָשׁוּט. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, הַכֹּל כְּמִנְהַג הַמְּדִינָה:
A plain get (bill, deed, etc.) [such as ours, which is not sewn and folded] — its witnesses (sign) on the inside [as we do]. And a folded get — (its witnesses sign) on the outside. [He writes one or two lines and folds it on the (inner) surface and sews, and one witness signs on the fold outside. And he writes another two lines or more on the inside and folds it on the surface, and a second witness signs on the fold outside, and so, a third witness. The rabbis instituted a folded get by reason of "irate Cohanim," who might write a divorce precipitously to their wives and regret it and not be permitted to take them back. A "folded get" was instituted for them, so that, not being able to write it quickly, they might calm down in the process. And just as "a folded get" was instituted for a bill of divorce, so was it instituted for other bills, the sages not differentiating in this regard.] A plain get, whose witnesses signed on the outside, and a folded get, whose witnesses signed on the inside — both are pasul (invalid), [not having been prepared as per rabbinic ordinance.] R. Chanina b. Gamliel says: A folded get whose witnesses were signed on the inside is kasher because it can be made plain. [i.e., If the sewing is undone and the get is opened, it becomes "plain."] R. Shimon b. Gamliel says: All is in accordance with the custom of the land. [The (practical) difference between the first tanna and R. Shimon b. Gamliel obtains in a place where both a plain get and a folded get are used, where one said: "Make me a folded get," and the other made a plain one, or vice versa. The first tanna holds that he is particular (that only the type he specified be used) and it (the other type) is pasul, and R. Shimon b. Gamliel holds that since the custom of the land is to use both, he is not particular.]
Bartenura on Mishnah Bava Batra
English Explanation of Mishnah Bava Batra
If in a simple document its witnesses signed behind, or if in a sewn document its witnesses signed within, they are invalid. Rabbi Hanina ben Gamaliel says: “If in a sewn document its witnesses signed within, it is valid, since it can be made into a simple document.” Rabban Shimon ben Gamaliel says: “Everything should follow local custom.”
The tenth chapter of Bava Batra deals with laws concerning the proper writing and execution of documents.
An “simple” document is one in which the text is written at the top of the page and the witnesses sign on the bottom, similar to forms used today. A “sewn” document is one in which a few lines of text are written, and then the text is folded over and sewn at the fold and then signed on the back of the document. This process is repeated several times, with each fold being witnessed and sign on the back side of the document. Evidently this was a more difficult type of document to forge. The first opinion in the mishnah states that each type of document must be signed in its customary manner: a simple document on the front and a sewn document on the back.
Rabbi Hanina ben Gamaliel states that a sewn document with signatures on the front is nevertheless valid, and is in essence treated as if it was a simple document.
Rabban Shimon ben Gamaliel states that this law is dependent on the customs of the place. If the custom is to allow sewn documents to be signed on the inside as well as the outside then they are valid; if not they are invalid.